1. Field of the Invention
The present invention relates to a method for driving a display cell equipped with rows of data electrodes and a plasma cell equipped with parallel discharge channels overlaid so as to comprise a flat plasma-addressed display device and more particularly relates to a method for controlling voltages applied to the data electrodes, anodes and cathodes.
2. Description of Related Art
A plasma-addressed display device of the structure shown in FIG. 8 has been previously disclosed in U.S. Pat. No. 4,896,149 to Buzak (Issue date: Jan. 23, 1990) or U.S. Pat. No. 5,077,553 to Buzak (Issue date: Dec. 31, 1991). The disclosure of the noted references are hereby incorporated herein. This plasma-addressed display device has a flat panel structure where an intermediate substrate 103 comprised of a thin glass sheet etc. is sandwiched between a liquid crystal cell 101 and a plasma cell 102. The plasma cell 102 is constructed using a lower substrate 104, with a plurality of parallel channels 105 being provided on the surface of the lower substrate 104. Each of the channels 105 are made air-tight by the intermediate substrate 103 with ionizable gas being enclosed so as to form individually separated discharge channels 106. Concave portions 107 between each of the channels 105 play the part of barrier ribs or ribs for dividing the individual discharge channels 106 and also act as gap spacers for the lower substrate 104 with respect to the intermediate substrate 103. Parallel pairs of electrodes 108 and 109 at the lower parts of each of the channels 105. These pairs of electrodes function as anodes and cathodes for ionizing the gas within the discharge channels 106 and for creating plasma discharges.
On the other hand, the liquid-crystal cell 101 is equipped with a liquid-crystal layer 111 sandwiched between the intermediate substrate 103 and the upper substrate 110, with stripe-shaped data electrodes being formed on the inner surface of the upper substrate 110. These data electrodes 112 are at right angles with respect to the discharge channel 106. Matrix-shaped pixels are therefore defined at the portions where the data electrodes 112 that act as rows of driving units and the discharge channels 106 that act as lines of scanning units cross-over with each other.
With this display device, the discharge channels 106 for carrying out the plasma discharges and the data electrodes 112 on the side of the liquid-crystal cell 101 are scanned simultaneously in a linearly sequential manner, with the desired image then being displayed by applying an analog data voltage. If a plasma discharge is created in the discharge channel, the approximate anode potential is maintained within the discharge channel. If a data voltage is then applied to the data electrodes 112 under these conditions, data may be written to each of the pixels of the liquid-crystal layer 111 via the intermediate substrate 103. When the plasma discharge is complete, the discharge channels 106 go to a floating potential and the written data is saved at each of the pixels. A so-called "sample-hold" operation is carried out, with the discharge channel 106 functioning as a sampling switch on the one hand and the liquid-crystal layer 111 functioning as a sampling capacitor. The liquid crystal is then operated in response to the sampled data and the lighting and extinguishing of the display devices is carried out in pixel units.
With the aforementioned panel structure, independently controlled anodes and cathodes are paired together so as to comprise a single discharge channel. However, each of the individual discharge channels are made to be air-tight by the intermediate substrate and the barrier ribs and construction is carried out in such a way that generated plasma does not leak over into adjacent discharge channels. Further, the driving waveforms are set-up so that the anode potential is taken as the value central to the maximum value and the minimum value of the data voltage. i.e. all of the anode electrodes are connected in common and maintained at a fixed potential. On the other hand, the cathode electrodes are sequentially scanned, with a sequential plasma discharge being generated every channel. However, 2n lines of electrodes (n lines of anodes and n lines of cathodes) are necessary to provide n discharge channels. Therefore, if a transmission-type structure is adopted for the plasma-addressed display device, there is a shortcoming in that the ratio of the display surface area occupied by the electrodes is increased, with the picture being covered by a corresponding extent, which results in the open area ratio being reduced. Because of this, a discharge channel structure to reduce the number of lines of electrodes by half was disclosed in, for example, Japanese Laid-open Patent Publication Hei. 4-265931. According to this publication, the number of lines of electrodes may be halved by adopting a structure where anodes and cathodes arranged alternately in a matrix are shared by respective adjacent discharge channels. In the following, this shall be referred to as the open-cell structure. It is therefore an object of the present invention to provide a driving method capable of selectively scanning discharge channels in a stable and efficient manner using an open-cell structure.